RU89783U1 - CURRENT LIMITER - Google Patents

Abstract

1. A current limiter comprising a reactor equipped with at least one secondary winding, the terminals of which are connected to at least one switching circuit of a fuse shunted by an explosive switch, the ignition input of which is intended to be connected to the source of the current limiting command. ! 2. The current limiter according to claim 1, in which the reactor and its secondary winding are made of superconducting material and placed in a cryostat. ! 3. The current limiter according to claim 1, wherein the explosive switch is shunted by a surge suppressor. ! 4. The current limiter according to claim 1, in which the switching circuit is connected to the terminals of the secondary winding of the reactor through a switch. ! 5. The current limiter according to claim 4, in which the control input of the switch is designed to connect to the source of the command for automatic restart. ! 6. The current limiter according to claim 4, in which the control input of the switch is intended to be connected to the current limiting command. ! 7. The current limiter according to claim 4, in which the switch is made in the form of an explosive contactor. ! 8. The current limiter according to claim 1, in which a means for setting the current limiting level, for example, an additional reactor, is connected to the terminals of the secondary winding of the reactor. ! 9. The current limiter according to claim 1, in which a voltage measuring transformer is connected to the terminals of the secondary winding of the reactor, the output of which is designed to be connected to a relay protection system and automation.

Description

Technical field

The proposal relates to the protection of electrical equipment against short-circuit currents (short-circuit currents) and, in particular, to means for limiting short-circuit currents in AC power networks.

State of the art

The development of the electric power industry - the introduction of new and expansion of existing power plants, an increase in the throughput of electric networks, leads to a constant increase in short-circuit currents in electric networks. Short-circuit currents at a number of power facilities (for example, in open switchgears of large power plants and substations with powerful transformer coupling) exceed the maximum breaking capacity of installed circuit breakers and even in some cases the maximum breaking capacity of any switching equipment currently in series production.

One of the effective ways to solve this problem is the use of high-speed controlled current limiters based on current-limiting reactors and switching current limiters, which reduce the short-circuit current to a value that can be switched by high-voltage switches installed on the corresponding power facility.

Known selected as a prototype current limiter containing a reactor, in parallel with which is connected a switching circuit in the form of a fuse, shunted by an explosive switch. The ignition input of the circuit breaker through a threshold element is connected to a current limiting sensor. The design, operation principle and application of such devices are described in [1, Fig. 3] and [2, Fig. 5].

The disadvantage of the prototype, which is especially pronounced when it is used in high-voltage circuits of electric networks, is the need to perform a switching circuit for a voltage that matches the voltage of the circuit in which current is limited. This disadvantage does not allow economically feasible to apply the known controlled limiters in high voltage networks with voltages above 35 kV. The proposed technical solution is aimed at eliminating this drawback.

Utility Model Disclosure

The technical result achieved is to improve the mass-dimensional characteristics of the current limiter, to be able to limit short-circuit currents in circuits whose voltage exceeds the voltage switched by the device. Using the proposed solution significantly expands the possibilities for optimizing the choice of installation sites of current limiters in the electric network, based on reliable and economic criteria.

The object of the utility model is a current limiter containing a reactor equipped with at least one secondary winding, the terminals of which are connected to at least one switching circuit of a fuse, shunted by an explosive switch, the ignition input of which is designed to connect to the source of the current limiting command .

This allows you to get the specified technical result.

The utility model has developments aimed at improving the operational and mass-dimensional characteristics of the current limiter. The development is that:

- the reactor and its secondary winding are made of superconducting material and placed in a cryostat;

- explosive circuit breaker is shunted by surge suppressor;

- a switching circuit connected to the terminals of the secondary winding of the reactor through a switch;

- the control input of the switch is designed to connect to the source of the command for current limitation or to the source of the command for automatic restart;

- means for setting the current limitation level, for example, an additional reactor, are connected to the conclusions of the secondary winding of the reactor;

- connected to the conclusions of the secondary winding of the reactor

voltage transformer, the output of which is intended for

connection to the relay protection system and automation.

Implementation of a utility model, taking into account its development

Figure 1 presents a diagram of a current limiter illustrating the implementation of a utility model, taking into account its development. The circuit contains a reactor 1 equipped with a secondary winding 2. One or several switching circuits 3 can be connected to the terminals of winding 2, each of which contains a fuse 4, shunted by an explosive switch 5. The ignition input 6 of the switch 5 is designed to connect to the source of the current limiting command . A current sensor installed in the primary or secondary circuit of reactor 1 and connected to input 6 via a high-speed control circuit, for example, a threshold element, can be used as the source of this command. Explosive circuit breaker can be performed, for example, in accordance with [3].

The reactor 1 and its secondary winding 2 can be made of superconducting material and placed in a cryostat 7.

The circuit 3 may contain a surge suppressor 8 (for example, a varistor or spark gap), a bypass switch 5.

Circuit 3 can be connected to the terminals of winding 2 directly or through switch 9. If there are several circuits 3 in the device, all of them, with the possible exception of one, are connected to winding 2 through switches 9. The control inputs 10 of switches 9 can be connected to the command source on automatic restart (AR) or to the source of the current limiting command.

To the conclusions of the winding 2 can be connected a means of setting the current limiting level, for example, in the form of an additional reactor 11, as well as a voltage measuring transformer 12, the output of which is intended for connection to a relay protection system and automation.

The device operates as follows.

The reactor 1 is connected with its primary winding sequentially in a limited current circuit, for example, in a power line. One of the switching circuits 3 (operating) shorts the conclusions of the winding 2 (directly or through a closed switch 9), and the remaining circuits 3 are separated by open switches 9.

In the normal mode of operation of the line with a shorted winding 2, the reactor 1 operates like a transformer in the short circuit mode of the secondary winding. The resistance introduced by the reactor 1 into the power circuit is minimal.

During short circuit on the line, the current through the reactor 1 and the current induced in the winding 2 increase many times, as a result of which the high-speed command source for current limiting, which controls the current in the line, feeds the input 6 of the isolator 5 installed in the operating circuit 3, providing a control signal that provides undermining of the circuit breaker 5.

As a result of the explosion, the circuit breaker 5 trips in a time substantially shorter than the half-period of industrial frequency. In this case, however, switching overvoltages do not occur, since the secondary short-circuit current passes to the fuse 4 circuit, bypassing the circuit breaker 5.

The current flowing through the fuse 4, provides a break of the fuse-link during the time determined by its time-current characteristic, which is selected so as to avoid unacceptable switching overvoltages on the one hand and, on the other hand, to open circuit 3 until the relay protection trips, which disconnects the line circuit breakers. The fulfillment of these conditions contributes to the shunting of the circuit breaker 5 surge suppressor 9.

If the winding 2 is not loaded, then after the switching circuit 3 is open, the reactor 1 operates as a transformer in idle mode. In this case, the resistance introduced by the reactor 1 into the power circuit is maximally determined by the reactor’s own inductance.

In the presence of a load connected to the terminals of the secondary winding 2, its resistance, reduced to the primary winding, shunts the resistance of the reactor 1. Maintaining a limited short-circuit current at the level, on the one hand, not exceeding the breaking capacity of the circuit breakers, and on the other hand, sufficient for subsequent operation relay protection can be provided by the appropriate choice of inductance of the additional reactor 11.

To issue a signal to the relay protection and automation system (RPA) about the state of the secondary winding 2 of the reactor (open or closed by a switching circuit 3), a voltage transformer 12 can be connected to the terminals of the winding 2.

One of the circuits 3 can be connected to the winding 2 either directly or through switch 9. The additional introduction of other (redundant) circuits 3, each connected through its own switch 9, improves serviceability and reduces emergency power outages.

After the relay protection is tripped and the circuit breakers installed on the power object turn off the short-circuit current limited by the proposed device, the signal at the output of the current limiting command source changes its value. A change in the signal can be used to put the next backup circuit 3 into operation. In this case, the switches 9 are controlled by the inputs 10 from the source of the current limiting command. In cases where the relay protection and control system issues a command to the automatic reclosure, the circuit breakers 9 can be controlled by inputs 10 from the source of this command.

Switch 4 and fuse 5 are single-action switches. To reduce the overall dimensions and ensure the comprehensiveness of the maintenance of the equipment, the switches 9 can also be used single-action switches - explosive switches made, for example, according to [4].

When the reactor 1 and its secondary winding 2 are made of superconducting material with placement in a cryostat 7, their superconducting state is maintained both in normal operation and in short-circuit mode. This reduces losses, reduces the mass and dimensions of the current limiter and avoids the need for fire hazardous oil cooling.

Information sources

1. P. Elagin. “Switching current limiters. New devices for protecting electrical equipment. " News of electrical engineering. Informational reference publication. No 4 (28) 2004

2. P. Elagin, A. Malyshev, Yu. Dementiev. “Switching current limiters. The main advantages of the application. " News of electrical engineering. Informational reference publication. No 1 (55) 2009

3. Explosive current breaker. RF patent №RU 2101795, IPC Н01Н 9/00, 1998

4. Explosive contactor. RF patent №RU 2076375, IPC Н01Н 39/00, 1997

Claims (9)

1. A current limiter comprising a reactor equipped with at least one secondary winding, the terminals of which are connected to at least one switching circuit of a fuse shunted by an explosive switch, the ignition input of which is intended to be connected to the source of the current limiting command. 2. The current limiter according to claim 1, in which the reactor and its secondary winding are made of superconducting material and placed in a cryostat. 3. The current limiter according to claim 1, wherein the explosive switch is shunted by a surge suppressor. 4. The current limiter according to claim 1, in which the switching circuit is connected to the terminals of the secondary winding of the reactor through a switch. 5. The current limiter according to claim 4, in which the control input of the switch is designed to connect to the source of the command for automatic restart. 6. The current limiter according to claim 4, in which the control input of the switch is intended to be connected to the current limiting command. 7. The current limiter according to claim 4, in which the switch is made in the form of an explosive contactor. 8. The current limiter according to claim 1, in which a means for setting the current limiting level, for example, an additional reactor, is connected to the terminals of the secondary winding of the reactor. 9. The current limiter according to claim 1, in which a voltage measuring transformer is connected to the terminals of the secondary winding of the reactor, the output of which is designed to be connected to a relay protection system and automation.